Heating apparatus



8 lSheets-Sheet 1 D. W. WILSON HEATNG APPARATUS FiledMarch 14, 1.952

June 17, 1941.

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`lune 17, 1941. D. w. wxLsoN HEATING APPARATUS Filed March 14, 1952 8 Sheets-Sheet 2 HNVENTOR- June' 17, 1941. D. w. wlLsoN HEATING APPARATUS Filed March 14 8 Sheets-Sheet 3 mmf INVENTOR- Alm. l

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ATTORNEY- 8 Sheets-Sheet 4 l I l i I l i .,llllJ D. W. WILSQNl HEATING APPARATUs Filed March 14, 1952 All.

June 17, 19541.

. INVENTOR- BY .1 W

IATTORNEY- June 17,r 1941. D. w. WILSON HEATING APPARATUS 8 Sheets-Sheet 5 Filed March 14, 1952 INVENTOR- ATTORNEY- www@ a+ W June 17, 1941.

D. W. WILSON HEATING APPARATUS 8 Sheets-Sheet 6 Filed March 14, 193g ATTORNEY- V \NN June 17, 1941. D. w. WILSON HEATING APPARATUS Filed March 14, 1952 8 Sheets-Sheet 7 AATTORNEY- June 17, 1941. D. w. WILSON HEATING APPARATUS Filed March 14, 1932 8 Sheets-Sheet 8 INVENTOR- ATToRNEY- Patented June' 17, 1941 anatre unirse srAras garant orifice HEATING APPARATUS Dustin W. Wilson, Elizabeth, N. J., assigner to Gasoline Products Company, Inc., Newark, N. J., a corporation of Delaware iipplication March 14, 193.2,Se1ial Nol 593,792 1s claims. (ci. 19e-5o) This invention relates to furnaces provided with radiant heating means and contemplates the provision of heating apparatusy constructed with a plurality of combustion or re chambers in order to furnish a greatly increased area of most effective heat absorbing surfaces. The major object of the invention is to provide a heating apparatus having a large area of most effective heat absorbing surfaces.

An equally important object of the invention is to provide a heating apparatus in which several streams of oil may be heated simultaneously and the temperature of each stream controlled by the provision of separate heating chambers' therefor. n

Another object of the invention is to provide a heating apparatus constructed as a single furnace having an oil heating duty in excess of anything previous.

With these and other objects in view, which maybe incident to the improvement, the inven-tion consists in the parts and combinations to be hereinafter set forth and claimed, vrith the understandingthat the several necessary elementscomprising the invention `may be varied in construction, proportions and arrangement without' departing from the spiritv and scope of the lappended claims. The invention broadly contemplates a unitary furnace structure provided with a plurality of re chambers, each of -which supplies radiant heat to elements arranged within thev furnace, andi-with a common convection chamber into which theY furnace gases from the several fire chambers are directed. y

lThe invention is particularly adapted for the heating of hydrocarbon oils and in this connection contemplates the provision oi a maximum amount of `radiant heating surface adapted for applying heat to the oil. V-

In Vorder to make the invention more clearly understood, there is shown inthe accompanying drawings, means for carrying the same into practical effect withoutlimiting the'improvements in their useful applications to the particular construction which, for the purpose of explanation, have been made the subject ofillustraticn.

In the drawings:

, Figure l is `a diagrammatic sectional elevation of a Iparticular embodiment of the invention showing heating means as applied to two separate streams of oil. l

Figures 2 and 3 are diagrammatic sectional elevations of modified apparatus also shown as adapted for heating two separate streams. of oil.

Figures 4 and?)` are'left and right-hand views, respectively,'in diagrammatic sectional elevation of another'modication shown as applied Vto the heatingof a single stream of oil. Y

Figure 6 is a iiow diagram in perspective illustrating a portion of the radiant 'heating section shown in Figure 4.

Figure 7 is a ow diagram in perspective illustrating a portion of the radiant heating section shown in Figure 5.

vFigures 8 and 9 are diagrammatic sectional elevations of particular embodiments of the invention showing heating means as applied to three separate streams of oil.

Referring to Figure 1, I 0 indicates a furnace or refractory setting which may conveniently be of box or rectangular shape. The furnace is provided With bridge Walls Ii and i2, which separate the furnace into combustion or rire .chambers I3 and I4 and a convection heating section I5. Burners are indicatedat I6 and I'I, in the fire chamber I3, and at I8 in the re chamber I4. A screen or balile wall I9, which may be vperforated, is placed intermediate vthe burners I5 and I'I` V One stream of oil to be heated may be admitted through an inlet 20 to a coil or tubular section 2I located in the'cooler section of the convection heating Zone I 5. The oil passes from the convection coil 2| to a coil comprising Wall tubes 22 disposed aboutY the walls of the iire chamber it. The coil 22 may well bedisposed about the four walls of the chamber consisting of one side of the bridge walls II and I2 and' the side walls of the furnace. The heated oil passes from the coil 22 through a coil of roof tubes 23 adapted to receive radiant heat from the re chamber I4, the oil being then discharged through outlet 2li.

The other stream of oil is shown asy being introduced to an inlet 25 to a convection heating coil Z positioned in the hotter portion of the convection heating zone I5. The oil Apasses thence through an intermediate radiant tube section 2'! disposed about the baiile I9. The oil is then directed through a Arow of wall tubes 23 disposed in the chamber yI3 along the other side of the bridge wall II and passes thence through iioor tubes 29 towall tubes 3B disposed adjacent one of the walls I0 of the furnace. The oil then passes through a, radiant heating coil 3I disposed about the four walls of the fire chamber I3 comprising the bridge wall II and three walls vof the furnace Ill. At the upper end of the bridge Wall 'II the four-wall tube section is changed to a three-Wall section 32, through which the oil passes to radiant roof tubes 33 and out through the outlet 34.

It is preferable to provide in addition to the burners I6, I1 and I8 corresponding burners entering from the opposite wall to that from which the burners I6, I1 and I8 enter. It is to be understood, however, that anynumber of burners may be employed without'departing Vfrom the scope of the invention. It is contemplated that the flames of the burners are projected inwardly and that the combustion gases rise in combustion chamber I3 to flow over the bridge wall II to be there contacted with the combustion gases rising in the combustion chamber "I4,- the combined gases then passing into the convection section to flow over the tubes in that section and finally passing to a ueior vchimney (not shown). the several surfaces, that is, the various wall tubes, floor tubes, roof ltubes and the tubes adjacent"the'-intermediate screennor bale I9 are heated' substantially by radiant heat while `the tubes located inV thechamber .I''are heated'by convection heat.'

The heating apparatus. of Figure 1 may be employed for various purposes, such for example, inthe cracking of `hydrocarbon oils, in which case both of the separate streams may be subjected to cracking temperatures, or if desired .onlyone of the streams may be brought to afcracking temperature while Vthe other stream may be more moderately heated. Inone exemplificationof the invention contemplated, one` of the` streams is employedas a high temperature cracking stream wherein `considerable f cracking 1 may -take y-place for the production of gasolinewhile the other stream may be 'subjected to a more `moderate temperature, such lfor exampla: as may be applied to a crude petroleumor residuum thereof for the purpose of enabling a moderate'degree of cracking for the breakinguor reducing of the viscosity of theoil.. The discharge pipes 34 and 24 may be connectedto suitable distilling apparatus or to such reaction chambers as may bedesired..

In the apparatus shownrin'Figure A2, a furnace Ia'is provided 'with bridge walls I la and' I2a to form fire chambers I3a and- Illa-and a convection chamber I5a. The flrechamber 13a is supplied with burners at I6a andv I'Ia, whilethefire chamber I4ais supplied with burners 48a. In one or more of the combustionwchambers, `such as is shown in the'combustion chamber I Saabafiles or screens I9a, similar to thebaflle I9, are disposed intermediate-the several-burners. The battles or screens may conveniently be vsupported on pedeStals 35.

The apparatus of Figure 2 is 'shown as applied to the heating of two separate streams of oil, one

of Iwhich is heated entirely by radiant heat and the other of which is heated partly by radiant heat and =partly by convectionfheaii Thus, one stream may -be introduced through an inlet 36 to arowo wall tubes 131 adjacent the bridge wall IIa; thence toa section of oor tubes 38, thence to intermediate radiant 'tubes 39 disposed about the'surfaoesof one of thescreens Ia, thence to another section of floor? tubes 4D," thence to another section of intermediate radiant tubes 4I disposed about the other screen 19a, thenceV to floor` tubes 42 and thence :to .a row of side wall tubes 43 along one of the Walls -Ia. The oil then passes through a section of four-walltubes 44 disposed about `the four walls of the combus- Thus, all of the tubes disposed alongV tion chamber I3a, including the bridge wall IIa. At the upper end of the bridge wall the four-wall tubes are changed to a three-wall section 45, from which the oil passes finally through roof tubes 46 to an outlet 41. Each section, other than the roof, of the several sections of coil just mentioned is shown as provided for dual flow, that is, each section consists of pairs of pipes inter-connected so that the oil flows in two parallel streams through the several pairs of tubes of which each section is composed. If desired, however, the arrangement may be such that there is ysingle flow entirely through all of the several coils. The stream thus introduced at the inlet 36 may be substantially entirely heated by radiant heat.

The other stream of oil enters through an inlet 48 through a coil section 49 positioned in a cooler section of the convection zone I5a, passes thence to a coil section 50 positioned in the hottest portion of the convection section I5a. The coil section 5I) may advantageously, although not necessarily, consist of only a comparatively small section of coil, such as the two rows indicated, and may form a screening section through which relatively low temperature oil may be passed to thusprotect the subsequent rows immediately underneath through which oil at a higher temperature may pass. The oil passes from the coil 5D to wall tubes 5I disposed adjacent the bridge wall I2a, thence through door tubes 52, thence through a row of Wall tubes 53 adjacent the bridge wall IIa, thencepthrough a fourwall section of tubes 54 which are disposed about the walls of the com-buston chamber I4a., including the bridge walls I Ia and I2a and the side walls of the furnace. The oil then passes through a section of roof tubes 55 and finally through a coil section 56 disposed in an intermediate portion of'the ,convection zone IEa and is iinally discharged through an outlet 51. The flow of oil oi this second stream is also shown to be dual.`

While the apparatus of `Figure 2 may be Aemployed for various purposes one advantageous application of this apparatus is in the carrying on of a combined crude reducing or a Viscosity breaking operation with a cracking operation for the production of cracked gasoline. Thus, for example, a heavy crude or reduced crude, which it is desired to skim or strip or to crack to a comparatively slight extent, such as in a mere viscosity breaking operation, may be introduced through the inlet 43 and passed through the several sections of the coil positioned in the radiant heating Zones of the fire chamber I4a and in the convection Zone I5a, the oil being then discharged through outlet 51 for distillation, while a cycle condensate obtained in the process may Ebe passed to the inlet 36 and passed through the several sections of radiant heat coils disposed about the several walls of the iire chamber I3a wherein the oil is cracked to the desired degree and may then be discharged through the pipe 41 into a reaction chamber for further cracking or passed directly to suitable distilling apparatus.

In the apparatus shown in Figure 3, there is a furnace IIlb provided with bridge Walls IIb and I2b to thus form fire chambers I3b and |412, and a convection chamber I5b, the re chamber i I3b being supplied with burners at IBb and IIb and nre chamber Ib being supplied with burner at IBI).

One stream to be heated may be admitted by an inlet line 58 to a coil section 59 positioned in a cooler section of the convection heating zone |b. The oil passes thence through a section of Wall tubes 60 disposed in the fire chamber |3b adjacent the bridge Wall Hb, thence through floor tubes 6|, thence through a row of tubes 62 adjacent the Wall |017, thence through roof tubes 63, thence through a section of coil 54 disposed in an intermediate section of the convection heating zone |517 and is iinally discharged through an outlet line 55.

The other stream of oil may enter through an inlet pipe 66 to a row of Wall tubes 61 disposed in the re chamber |429 adjacent the bridge Wall |2b, thence to another section of Wall tubes 68 adjacent the bridge Wall Hb, thence through roof tubes 69, thence through a coil section disposed in the hotter section of the convection zone |5b, the oil being finally ldischarged through outlet pipe 1|.

The flow of oil through the several sections of coil shown in the apparatus of Figure 3 is indicated as being in dual streams through each section, that is, each section of pipe is shown as consisting of pairs of tubes inter-connected in series.

One advantageous operation that may be carried on with the apparatus of Figure 3 is to conduct a combined vacuum distillation and atmospheric or superatmos'pheric pressure distilling operation. Thus, the stream for the vacuum distilling unit may advantageously be introduced through the line E5 and discharged by the line 1| to the vacuum flashing or distilling chamber While the other stream may be admitted through the line 58 and discharged through the line 65 to suitable distilling apparatus operating under atmospheric or superatmospheric pressure.

In Figures 4 and 5, a furnace or refractory setting |06 is provided with bridge Walls ||c and to form combustion chambers |30 and Mc and a convection heating section |50. The re chamber is supplied With burners at |60 and |1c and the iire chamber Hic is supplied with burners at |8c. Intermediate the several burners and |10 in the fire chamber |30 are baiiles or screens |90, which may be suitably supported on pedestals 35e. Intermediate the several burnn ers in the fire chamber |00 are baiiles or screens 12, Which may Fbe suitably supported on pedestals 13.

The stream of oil to be treated in the apparatus of Figures 4 and 5 enters through an inlet line 10 to a section of coil 15 positioned in the convection heating zone |50. The iiow of oil through the coil 15 is indicated as being in quadruplet. through a connecting line 15 having branches 16, 11, 1S and 19. The oil in branch line 15 passes to a side Wall section of tubes 80 in the combustion chamber I 4c adjacent the bridge wall |2c, thence through floor tubes 0 I, thence through lubes 82 disposed along the surfaces of one of the` ballles 12, thence through an additional section of Hoor tubes 83 to a transfer line 04. The stream of oil entering the branch line 11 passes through wall tubes 85 in the re chamber |40 adjacent one side of the bridge Wall Hc, thence through floor tubes 85, thence through a section coil 81 disposed about the other baiile 12, thence through oor tubes 80 to a transfer line 89. The oil entering the pipe 1B passes through Wall tubes 90 disposed along the other side of the bridge Wall Hc in the combustion chamber |3c, thence through floor tubes 9|, thence through tubes 92 disposed along the surface of one of the intermediate screens and thence through addi- The oil passes from the coil 15 tional floor tubes 93 to atransfer line '94. The oil entering the other branch line 19 passes through Wall tubes 95 adjacent one of the outer Walls |0c, thence through oor tubes 90, thence through tubes 91 disposed along the surface of the other intermediate screen |9c, thence through floor tubes 98 to transfer line 99.

The streams in the transfer lines 84 and 89 are merged in a line |00 for delivery to a fourwall coil section |0| disposed about the Walls in the iire chamber Mc, including the fbridge Walls l ic and |'2c and the side Walls of the furnace, the oil flowing in dual ow through the coil |0|. The oil then passes in dual flow through a threewall section |02 along the surfaces of the com'- bustion chamber |4c, including the bridge wall ||c and the side walls of the furnace. The oil then passes to a two-Wall section |03, one of the dual streams of oil from the coil |02 passing through one of the side Wall coils |03 and the other stream passing through the other side Wall coil |03, these side wall coils being located on opposite Yfurnace Walls in the fire 'chamber |40. The oil finally passes to roof tubes |04 in dual flow and thence to an outlet pipe |05.

The streams of oil in the lines 94 and 99 are merged in the line |06 by which they are Vconducted to a four-Wall coil |01 disposed about the walls of the re chamber |3c, including three Walls of the furnace and the bridge wall ||c. The oil passes thence through a three-Wall section of coil |08 disposed about the three Walls of the furnace. Finally the oil passes through roof tubes |09 to outlet ||0. The flow of oil through each of the coils |01, |08 and |09 is shown in dual flow.

The apparatus illustrated in Figures 4 to '1 is particularly adapted for the cracking of hydrocarbon oils, and it is contemplated that the oil at cracking temperature may be delivered through the transfer lines |05 and |||J to a suitable reaction Vessel or to a suitable distilling apparatus or both.

In the apparatus shown in Figures 8 and 9, there is a furnace lild provided with bridge Walls and ||2 to form re chambers H3 and ||4 and a convection chamber H5. I'he nre chamber I3 is supplied with burners at 6 and i1 and the re chamber ||4 is supplied with burners at ||8 and H9. V

The apparatus of Figure 8 is shown as applied to the heating of three streams of oil, all three of which are heated partly by radiant heat and partly by convection heat.

One stream of oil to be heated may be admitted by an inlet pipe |20. then passed to a coil section |2| positioned in a part of a cooler section of the convection heating zone H5. The stream then passes through a section of wall tubes |22 disposed in the iire chamber H3 adjacent the Wall thence to another section of Wall tubes |23 and thence to a radiant heating coil 520 disposed about the four Walls of the lire chamber H3, comprising the bridge Wall and three Walls of the furnace |0d. The oil then passes through radiant roof tubes |25, thence through a section of coil |25 disposed in a part of a hotter section of the convection zone 5 and is nally discharged through an outlet pipe |21.

The tubes in the convection zone H5, just described, extend from the bridge Wall to ap'- proximately the center of the convection zone. Corresponding portions of the convectionY zone ||5 from the bridge Wall H2 to the center of the convection zone receive tubes now to be described.

The second stream of 'oil may enter through an inlet pipe |28, then passed to a coil section |29 positioned in the other part of the cooler section of the 'convection zone H5. The oil then passes through a section of wall tubes |30 disposed in the rire chamber H4 adjacent the bridge Wall |I2, thence through another section of wall tubes |3| and thence to a radiant heating coil |32 disposed about the four walls of the fire chamber H4, comprising the bridge wall H2 and three walls of the furnace Id. The `oil then passes through radiant roo'f tubes |33, thence through a section of coil |34 Adisposed in the other part of the hotter `section of the convection zone and is discharged through an outlet pipe |35.

The tubes above described as being in the convection zone H5 provide an arrangement whereby' each stream of oil may be heated by convection heat independently of the other. As is shown, the coil section |2| and the coil section |29 extend to the center of the convection zone -H5 and consist of the same number of tubes. The same is true of the coil sections |26 and |34. By this arrangement it is possible to divide the convection zone H5 vertically into two sections for heating a diierent stream of 'oil in each section. Thus, it will be seen that different streams of oil entering the inlets and |28 are subjected to the same heating in the convection zone H5 and may be heated to any desired temperature in the radiant heating zones or fire chambers H3 and H4.

While the coil sections |21 and |29 and the coil sections |26 and |34 have been shown and described as consisting of the same number of tubes and occupying corresponding portions of the convection zone, it is to be understood that this invention is not limited to this arrangement. Each section of coil may be arranged in a manner best suited for subjecting a plurality of streams of oil to diierent temperatures.

The third stream of oil to be heated may be admitted through an inlet pipe |38 and thence to a coil section |31 positioned in a cooler section of the convection heating zone. The oil then passes through radiant roof tubes |38 disposed in the radiant heating zone H3, thence through similar radiant roof tubes |39 in the radiant heating zone H4 and is discharged through an outlet line |40.

The coil sections |31, |38 and |39 are shown as connected for single flow; the coil sections |22 to |25 and |29 to |33, both inclusive, are shown as connected for dual flow; and the coil sections |26 and |34 are shown as connected for triple iiow. Obviously this manner of arranging the tubes of the various coil sections may be varied without departing from the spirit of the invention.

The apparatus shown in Figure 8 may be employed for various purposes. For instance, crude oil or a reduced crude may be introduced into the inlet pipe |20 and raised to a high or cracking temperature in the fire chamber I3. A cycle condensate obtained from a cracking operation may be introduced into the inlet pipe |28 and also raised to a high or cracking temperature. Into the inlet pipe |36, naphtha or gasoline may be introduced and subjected to convection heat in the convection zone H5 and then subjected to radiant heat in the roof tubes |38 and |39 in the radiant heating zones H3 and I4. The temperature of the naphtha or gasoline leaving the voutlet |40 may be governed by regulating its flow through the heating coils thereby obtaining reformation of the gasoline or naphtha. It is to be understood that this invention is not limited to the above method of operation. The invention broadly comprehends introducing three streams of oil into a furnace, governing the temperature of two of the streams by regulating the heat produced by the burners in the radiant heating Zones and governing the temperature of the third stream oi oil by regulating the quantity of flow through the coil in the convection zone.

The heated streams of oil 'discharged through the outlet pipes |21, |35 and |40 may be passed to any suitable apparatus where further treatment thereof may be carried out.

The apparatus of Figure 9 is shown as applied to the heating of three streams ci oil, two of which are heated by radiant heat in the re chambers H-3 and H4 and the third of which is heated solely by convection heat in the convection heating zone H5.

One stream of oil to be heated may be admitted by an inlet pipe |4|, then passed to a section of wall tubes |42 positioned in the fire chamber I3 adjacent the bridge wall |H, thence to another section of wall tubes |43 and thence to a radiant heating coil |44 disposed about the four walls of the re chamber H3 comprising the bridge wall H| and three walls of the furnace Mld. The oil then passes through radiant roof tubes |45 and thence out through an outlet pipe |45.

A second stream of oil tc be heated follows the same path through the fire chamber H4. The second stream may be admitted by an inlet pipe |41 then passed to a section of wall tubes |48 positioned in the rire chamber H4 adjacent the bridge 'wall l I2, thence to another section of IWall tubes |49 and thence to a radiant heating coil |58 disposed about the four walls of the fire chamber H4, comprising the bridge `wall H2 and three walls of the furnace Mid. The oil then passes through radiant roof tubes |5| and thence out through an outlet pipe |52.

A third stream of oil may be heated entirely in the convection lzone H5. This third stream may be admitted through an inlet pipe |53, thence through a coil section |54, positioned between the bridge walls HI and l2 and thence out through an outlet pipe |55.

One method of operating the apparatus shown in Figure 9 is to introduce a heavy oil into the inlet pipe |4|. The oil is then raised to a high or cracking temperature in the fire chamber H3 and is discharged through the outlet pipe |46. A light oil may be introduced into the inlet pipe |41, raised to a high cr cracking temperature in the re chamber l I4 and then discharged through the outlet pipe |52. The two streams of oil leaving the outlet pipes |46 and |52 may be passed to any suitable distillation or cracking apparatus or both, Vwhere the contemplated methods of treating the two streams of oil is consummated.

A third stream oi oil, such as reduced crude. may be introduced into the inlet pipe |53 and passed through the coil section |54 positioned in the convection zone I5. The oil passing through the coil section |54 may be raised to a temperature sufciently high to accomplish viscosity breaking thereof. The temperature of the oil may be governed by regulating the quantity flowing through the tubes. The heated oil is then discharged through the outlet pipe |55 to any suitable apparatus for further treatment, or if desired, to storage.

' heat applied in the With the arrangement shownin Figures 8 and 9, hree streams of iiuid may be heated todifferentv temperatures to carry out any desired operation for each stream. Or if desired two of the streams may be heated to the same temperature and the third stream to a different temperature.

The baiiles or screens positioned in the re chambers for supporting additional heating coils, may be perforated if desired. By perforating the baliles or screens, it is possible for the hot gases of combustion to pass through the sections of coil positioned adjacent the surfaces of the baffles or screens. By this expedient, additional heating of the oil passing through these sections of coil may be accomplished.

An important feature of the invention is the provisionV of unitary heating, apparatus of maximum capacity. This feature is particularly exemplied inthe apparatus of Figures l to 7 in Whicha furnace, structure is provided of considerably greater capacity than has hitherto been possible.

It is contemplated that in the apparatus shown, additional burners, may be provided as on the opposite walls from` those in which the burners are placed, In the Several structures shown in these several figures the various radiant heating tubes located adjacent the interior surfaces of the fire chambers are preferably placed substantially out of the 4path of the convection gases so that they o may not be subjected to direct convection heat in the lire chambers and are heated by the radiant heat afforded by the several burners in the lire chambers.A It is contemplated that the furnace gases after being passed from the fire chambersnto one of the oonvectionzones andA after flowing over the elements to be heated therein may be passed to a suitable flue, or chimney, notshown. In one method of operationV contemplated by the invention, the convection heating section may be eliminated and the furnace gases which aredischarged from the nre chambers may beemployed in preheating the air supply to the burners.

The separate control of the degree of radiant several radiant heating` zones, provided by the invention is an advantageous feature thereof, particularly inthe case of cracking operations. Thus, the oil streampassing through the furnace maybe rapidly raised to a cracking temperature and the soaking heat required in the nal sections of the coil may be very accurately controlled in accordance with my invention.

YAn important method of operation contemplated by the invention is to heat separate streams of oil which may have different characteristics requiring different degrees of heat for cracking in separately controlled radiant heating sections. Thus for example, in the apparatus of Figure 1, one stream of oil after preferably being preheated in the convection coil 26 may be passed through the radiant conduits positioned in the fire chamber I3 while another stream of oily afterbeing preferably preheatedvin the convection coil 2| may be passed through the radiant heating conduits of the re chamber Ill, the reY chambers I3 and I4 being separately controlled so that the desired cracking temperature may be appliedin each instance. The two separate streams of oil may be derived from various sources, thus, one stream may be raw charging stock while the other may be cycle condensate obtained in the process or both streams may be withdrawn from the fractionating zone of the systemw but removed from dierent pointsl therein, Intheapparatus of Figures 4 and 5, for example,

' without departing two cuts may be withdrawn from the'fractionating zone, one cut being passedl through the raviant heating conduits of the re chamber |30 While the other stream may be passed through the radiant heating conduits of the fire chamber Ido or if desired a greater number of cuts of varying boiling points may be Withdrawn from the fractionating zone and passed through separately controlled radiant heating zones of the furnace.

It is to be understood that this invention comprehends that the tubes may functionv to shield a part or all of the interior surfaces of the furnace adjacent which they are positioned to such an extent that they will radiate little or no heat, although if desired, the arrangement may be such that the walls may function as heat radiating or reflecting surfaces.

While there is shown and described the preferred embodiments of the invention and speciflc examples of operation for each, it is to be clearly understood that the invention is not to be limited by the precise details of construction herein set forth, by way of illustration, as itis apparent that many changes and variations may be made therein, by those skilled in the art,

from the spirit of the invention, or exceedingV the scope of the appended claims.

I claim:

1. A heating apparatus of the character des ribed comprisinga plurality of separately fired fire chambers, a convection chamber for receiving hot gases of combustion from said fire chambers, a, coil for heating a streamV of :duid passing therethrough and extending through a portion of the convection chamber and along the walls of one of the re chambers, a second coil for heating another stream of fluid passing therethrough and extending through another portion of the convection chamber and along the walls of another fire chamber and a third coil for heating anotherY stream of :duid passing therethrough and extending through another portion of the convection zone and each of said re chambers.

2. The method of heating a plurality of streamsY of oil in a unitary heating apparatus which comprisesintroducing` one stream of oil into a portion of a convection heating zone and passing said stream of oil into a separately fired radiant heatingl zone, introducing a` second stream of oil into another portion of the convection heating Zone and passing said second Stream into another separately red radiant heating zone, and introducing a third stream of oil into still anotherV portion of the convection heating zone and subjecting said third stream to radiant heat in both of the radiant heating zones.

3. A unitary furnace for heating hydrocarbon iiuids which comprises a plurality of separately fired re chambers, separate yinterconnected conduit elements forming separate coils, for conveying hydrocarbon uid being heated disposed in each of said fire chambers and adapted to be heated preponderantly by radiant heat from furnace gases therein, a convection heating chamber connected to and'A disposed between said fire chambers to receive furnace gases therefrom, conduit elements disposed in said convection chamber and connected to form a pluralityv of separate coils therein, separate means connecting a separate coil in each of said separately flred re chambers to a separate coil in said convection chamber and other meansconnecting anotherseparate coil in at least one of 6 the ire chambers to another of the separate coils in said convection chamber.

4. A unitary furnace for heating hydrocarbon iiuids which comprises a plurality of separately iired re chambers defined by walls, roof and a floor, separate heating coils for conveying hydrocarbon fluid being heated separately disposed, respectively, on the walls and roof in each of said fire chambers and adapted to be heated preponderantiy by radiant heat from furnace gases therein, a convection chamber connectedto and disposed to receive furnace gases from each of said fire chambers, a plurality of separate heating coils in said convection heating chamber for conveying a separate stream of hydrocarbon fluid through each, means connecting a heating coil disposed on the walls in each of said fire chambers to a separate heating coil in said convection heating chamber and means also connecting the heating coil disposed on the 'roof in at least one of the fire chambers to another separate coil in said convection heating chamber.

5. A unitary furnace for heating hydrocarbon iuids which comprises a plurality of separately fired fl-re chambers, each of which is defined by walls, a roof and a iioor, a separate heatingl coil for conveying hydrocarbon fluid bei-ng heated comprising a plurality of separate interconnected heat absorbing tubes disposed along the walls of each of said re chambers and adaptedto be heated preponderantly byl radiant heat from furnace gases therein, a convection heating chamber connected to and disposed to receive furnace gases from each or said fire chambers, and a separate heating coil in said convection heating chamber having an extension in eachof said fire chambers, each of said aforementioned heating coi-ls being adapted toconvey a separate stream of hydrocarbon flu-id therethrough.

6. The method of heating a plurality of streams of oil in a unitary heating apparatus whichcornprises introducing one stream of oil into a heat-- ing apparatus and heating it in a separately red heating zone preponderantly by radiant heat mainly from furnace gases producedl therein, conducting the thus heated oil into a convection heating zone wherein convection heat is imparted thereto, introducing another stream of oil into the convection heating zone wherein convection heat is impartedthereto and passing said last mentioned stream into another separately fired heating zone separated and apart from the aforementioned heating zone wherein it is further heated preponderantly by radiant heat mainly from other furnacegases produced therein, the convection heat for said convection heating zone being derived from furnace gases received from said separately fired heating zones.

TQTh-e method of heating a plurality of streams of oil in accordance with claim 6 wherein the last mentioned stream of oil is conducted from the separately fired heating zone through which it passes to said convection heating zone wherein it is further heatedby convection heat.

8-. The method of heating a plurality of streams of oil ina unitary heating apparatus which `comprises -introducing one stream of oil into a convection heating -zone wherein convection heat is, iin-parted thereto, passing saidstream to a separately fired radiant heating zone and conducting it through tubes along the walls thereof and heating said stream iin passing through said radiant heating zone preponderantly by radiant heat mainly from `furnace gases produced there- 7d in, conducting the thus heated oil to the convection heating Zone, introducing a second stream into the convection heating zone wherein convection heat is imparted thereto, passing said stream to another separately red radiant heating zone separated and apart from the aforementioned radiant heating zone and conducting it through tubes along the Wall-s thereof and heating said second stream in passing through the last-mentioned radiant heating zone preponderantly by radiant heat mainly from furnace gases produced therein, the convection heat for said convection heating zone being `derived from furnace gases received from said separately fired radiant heating zones.

9. The method of heating Ia plurality of streams of oil in a unitary heating apparatus which comprises introducing one stream of oil into a convection heating zone wherein convection heat is imparted thereto, passing said stream to a separately fired radiant heating zone and conducting it ,through tubes along the walls and roof thereof and heating said stream inpassing through said radiant-heating zone preponderantly by radiantheat mainly from furnace gases produced therein, conducting the thus heated oil to the convection heating zone, introducing a second stream into the convection heating zone wherein convection heat is imported thereto, passing said stream to another separately fired radiant heating zone separated and apart from the aforementioned radiant heating Zone and conducting it through tubes along the walls and roof thereof and heating said second stream in passing through the last-mentioned radiant heating zone preponderantly by radiant heat mainly from furnace gases produced therein, the convection heat for saidconvection heating zone being derived from furnace gases received from said separately red radiant heating zones.

1G. The method of heating a plurality of streams of oil' in accordance with ciaim 8 wherein the stream of oil' is conducted from the lastmentionedseparately fired radiant heating zone .to the convection heatingv zone wherein additional heat is imparted thereto.

11. The method of heating a plurality of streams of oii .ina unitary heating apparatus which comprises introducing one stream of oil into a convection heating zon-e wherein convection heat is 'imparted thereto, passing said stream to a separately fired radiant heating zone and conducting it through tubes along the walls thereof and heating said stream in passing through said radiant heating zone preponderantly by' radiant heat mainly from furnace gases produced therein, passing said stream of oil from said radiant; heating zone to said convection heating zone wherein additionalconvection heat is imparted thereto, introducing a second stream of oil directly intoanother separately fired radiant heating zone separated and apart from the aforementioned radiant ing it through tubes along the walls thereof and heating said second stream in passing through the last mentioned radiant heating zone preponderantly by radiant heat mainly from fuma-ce gases produced therein, passing said second stream from said last mentioned radiant heating zone to said convection heating zone Wherein additional convection heat' is imparted thereto,the convection heat for said convection heating Zone being derived from furnace gasesV received from said separately firedl radiant heating zones.

12. The method of heating a plurality of heating zone and conduct-f thereof and heating said stream in passing through said radiant heating zone preponderantly by radiant heat mainly from furnace gases produced therein, introducing a second stream linto the convection heating zone wherein conveotion heat is imparted thereto, passing said stream lto another separately fired radiant heating zone separated and apart from the aforementioned radiant heating zone and conducting it through tubes along the walls thereof and heating said second stream in passing through the last-mentioned radiant heating zone preponderantly Aby radiant heat mainly from furnace gases produced therein, and passing a third stream of oil through said convection heating zone and conducting the third stream of oil through part of each of the radiant heating zones to be therein heated preponderantly by radiant heat, the convection heat for said convection heating zone being derived from furnace gases received from said separately fired radiant heating zones.

I13. In a furnace having a plurality of combustion sections and a communicating convection heat section through which combustion gases from the `combustion sections are passed thereby forming in the convection section a zone of high rate of heating .and Ia zone of lower rate of heating, the combination of a iiuid conduit in each of the combustion sections, a tube bank in .the convection section land having tubes in both said zones, means for passing two parallel streams of fluid through the tub-es in said zone of lower rate of heating and for then passing one of said streams of uid through said conduit in one combustion section and for passing the other stream through said conduit in another combustion section and at least through some of the tubes in said zone of high rate of heating.

14. In the heating of hydrocarbon oils to conversion temperatures, the method which comprises passing a relatively heavy oil first through a convection "section and thence through a radiant heat section of a furnace wherein radiant heat is generated and subjecting the same during such ow to a high rate of heating, simultaneously passing a lighter oil through a second radiant heat section in said furnace wherein radiant heat is generated for heating the lighter oils, then passing the lighter oil through said convection section of the furnace, and passing combustion gases from both said radiant heat sections in indirect heat exchange relation with the oils in the convection section.

15. In the heating of hydrocarbon oils to conversion temperatures, the method which comprises passing a relatively heavy oil lrst through a convection section and thence through a radiant heat section of a furnace wherein radiant (heat is generated for heating the relatively heavy oil, simultaneously passing a lighter oil through a second radiant heat section in said furnace wherein radiant heat is generated for heating the lighter oil, then passing the lighter oil through said convection section of the furnace, and passing combustion gases from both change relation with said radiant heat sections in indirect heat exthe oils in the convection section.

16. A process of heating hydrocarbon oils comprising the steps of burning fuel in a rst combustion zone to generate radiant heat and hot gases of combustion, independently burning fuel in a second lower temperature combustion to generate radiant heat and hot gases of combustion, separately withdrawing the hot gases from commingling them with drawn from the second combustion zone, simultaneously passing hydrocarbon oil in an elongated confined stream through the zone containing the tempered commingled7 gases to thereby heat the oil mainly by the convection heat of the gases and then passing the oil in a confined stream through the combustion zones of successively higher temperature to thereby progressively heat the oil mainly by the radiant heat generated in each.

17. In a furnace having a pair of independently fired combustion zones, and a convection Zone adapted to receive furnace gases from said combustion zones, the combination of a plurality of heating tubes in said convection zone forming a plurality of coils for the passage of separate streams of fiuids, a plurality of heating tubes in each of said combustion zones forming a continuous heating coil therein having a section thereof adjacent the roof, means for connecting a separate coil in said convecbustion zones for the passage of another separate stream of fluid therethrough and other means for connecting a heating coil in at least one of said combustion zones with still another separate coil in said convection zone.

18. In the heating of hydrocarbon oils to conversion temperatures in furnaces having a pair of independently red combustion and radiant heat zones provided with uid conduits and a convection heating zone receiving combustion gases from both said combustion zones and having tubes in the path of flow of the combustion prises passing a relatively light oil and a heavier oil in separate parallel streams through tubes in said zone of lower rate of heating, passing the oil through fluid conduits in one of said combustion zones and through tubes in said zone of higher rate of heating and passing the heavier from said tubes other of said combustion zones.

DUSTIN W. WILSON. 

